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The humble water heater could be the savior of our energy infrastructure woes

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Re: The humble water heater could be the savior of our energy infrastructure woes

#151

Post by OliverJones »

This article contains two suggestions:

1. heat pumps rather than resistance heating: move the heat where you want it instead of creating it from scratch.

2. timeshifting electrical load. Figure out how to add and shed it on demand.

The second one has a remarkable property. Load can be shed much more quickly than spinning up peak-load generators. That means grid operators can, in periods of overload, keep the grid's AC frequency (50 or 60Hz) from dropping. Without load shedding it's done with expensive and dirty peak-load generators. That's called "frequency control ancillary services" (FC/AS) in the grid biz, and it's economically important: regional grids don't work properly unless their local grids all run at the same frequency. Local grids don't want to be disconnected from regional grids in peak-load times because their generators slowed from 60Hz to 59.8Hz. Remotely switching off a mess of hot water heaters is a GREAT way to change the grid load quickly if that starts to happen.

FC/AS is a major driver of the big Australian battery projects (built with parts from Tesla). https://www.greentechmedia.com/articles/read/australia-picks...

Who is the Van Jacobson (TCP designer who dreamed up slow-start / exponential backoff) of smart grids? Is it somebody reading HN?

Re: The humble water heater could be the savior of our energy infrastructure woes

#152

Post by guerby »

nine_k wrote: post #62
selectodude wrote: post #52

Earlier quoted context omitted.

There is a large building in Chicago that basically contains a giant ice cube. https://www.enwave.com/locations/chicago.htm

From their website I gleaned that they have 5 facilities, and several miles of piping that carries ice-cold water to their customers, large buildings around. It's the maximally outsourced air-conditioning solution I ever saw :)

Paris has a large cold water network:

https://www.climespace.fr/en

It's used by some datacenters IIRC.

Re: The humble water heater could be the savior of our energy infrastructure woes

#153

Post by PeterisP »

elric wrote: post #104
jcynix wrote: post #97

Earlier quoted context omitted.

Good heat pumps aren't of the air conditioner type. Our heat pump uses two 60m deep drilled holes. Thus heat exchange happens in the ground, which is always more or less 10 degrees Celsuis. Heat exchange in the house happens through floor heating. So during a hit summer, the reverse capability just pumps the cold water through our floors (controlled for the dew point) and the warm floor water into the ground. That, c…

> Good heat pumps aren't of the air conditioner type. Our heat pump uses two 60m deep drilled holes. Thus heat exchange happens in the ground, which is always more or less 10 degrees Celsuis. Good point. The source and destination of heat can be air, water, or "ground source". But it's still all just the same concept as A/C units. Pump heat to one place, using less energy than what it would take to heat it using resi…

The special thing about ground source heat pumps is, well, that they use ground instead of air - and it turns out to be a really important thing because of the temperature differences between ground and air.

A/C or heat pump efficiency is directly related to the temperature difference over which you're trying to pump. If the temperature difference is twice as large, you need to spend twice as much energy to pump the same amount of heat.

Furthermore, the days where you need a heat pump (or A/C) the most are the peak cold/heat days where the temperature difference between your house and the air is much larger than usual. Because of this, a ground source heat pump can do the same thing by spending much less power than an air source heat pump, so it is "greener" - though the installation is more cumbersome and expensive.

Re: The humble water heater could be the savior of our energy infrastructure woes

#154

Post by benhurmarcel »

jdsully wrote: post #33
temporallobe wrote: post #29

I have a tankless hot water heater system in my new home that runs on a city natural gas line. It’s super efficient and thus my energy bills are very low compared to what I used to pay for the traditional electric hot water heater in my previous home, however it’s not a silver bullet. I find myself running the water for a ridiculously long time in order for the water to start getting hot, sometimes for more than a mi…

The majority of your savings are from switching to gas from electric. Gas is significantly cheaper per BTU. Gas tank heaters are still pretty efficient. Especially if insulated.

Using gas generates fixed additional costs though, apart from the energy price. You have to pay an additional provider fee, the annual maintenance of the gas heater, regularly change the CO detectors, etc.

It's worth it for a larger volume though. Not so much for a small flat.

Re: The humble water heater could be the savior of our energy infrastructure woes

#155

Post by benhurmarcel »

coryrc wrote: post #128
jnsaff2 wrote: post #93

Earlier quoted context omitted.

I live in a cool place. This winter we had extended periods of -20C. Heat pump efficiency drops, but still stays above 2. SCOP (for year round average for heating coefficient of performance) units sold now are better than 5. Also, if you are worried about the refrigerant leaking, you can sacrifice a little bit of efficiency and buy a unit using CO2 as a refrigerant with a GWP of you know: 1. I think the biggest probl…

If the hot water heat pump is a single unit (which is the vast majority of residential installations) and indoors, it is just stealing heat from your regular heating system. You're paying for that heat, so you aren't getting COP > 1.

You're only paying for that heat in the winter though.

Re: The humble water heater could be the savior of our energy infrastructure woes

#156

Post by [deleted] »

elil17 wrote: post #45

Another type for thermal battery: ice thermal storage. Instead of running AC, it’s a freezer that makes ice during the night (using off-peak electricity and taking advantage of the cooler nighttime air) and then melts it during the day to cool large buildings. They’re a ridiculously good idea if you’re running a large enough HVAC system - they can even lower capital costs compared to traditional systems. Unfortunatel…

[deleted]

Re: The humble water heater could be the savior of our energy infrastructure woes

#157

Post by paul_f »

cycomanic wrote: post #88

In Northern Europe heat pumps are now pretty much standard for new homes. They reduce heating bills quite dramatically compared to other technology. In particular if combined with solar power. One big advantage is that they can also be run in reverse so you could cool the house in summer (although you might need a special heat pump to do this, especially to separate from the hot water). In areas where it gets very co…

Europe has milder winters than many parts of the world. A downside of a heat pump is the limitation on temperature range. A heat pump could never be used in Minnesota, people would freeze.

Re: The humble water heater could be the savior of our energy infrastructure woes

#158

Post by archi42 »

kwhitefoot wrote: post #131

Meanwhile the EU is intending to ban hot water tanks in favour of instantaneous heaters.

Source? For solar heating you'll want one to store excess heat collected during the day.

With (grid sourced) electricity as the only energy source for the heat - and in absence of a "smart grid" - storing hot water adds losses, compared to heating the water just in time. So I can understand why they might think about some sort of ban.

If they go for a ban, I'd expect them to add some conditions.

Re: The humble water heater could be the savior of our energy infrastructure woes

#159

Post by chiph »

elric wrote: post #92
cycomanic wrote: post #88

In Northern Europe heat pumps are now pretty much standard for new homes. They reduce heating bills quite dramatically compared to other technology. In particular if combined with solar power. One big advantage is that they can also be run in reverse so you could cool the house in summer (although you might need a special heat pump to do this, especially to separate from the hot water). In areas where it gets very co…

> One big advantage is that they can also be run in reverse I don't get why this is an advantage. That's just plain old air conditioning, which is genreally considered to be a wasteful, energy guzzling luxury in colder climates. The heat pump hype is a bit puzzling to me. Here's a TreeHugger article which puts it better than I can: https://www.treehugger.com/why-are-there-so-many-fist-pumps-...

Yes, air-exchange heat pumps have been around forever. But they're usually of the all-the-way-on or all-the-way-off type in the US. Newer systems use variable refrigerant flow and variable fan speeds to save energy, so they run more proportionally to the heating/cooling load. They have a higher up front cost so production builders don't put them in, but custom home builders will.

In cold climates you eventually hit an efficiency wall with the air-exchange units and need to use a ground-source heat pump, with glycol pipes being run deep in the ground to exchange heat. And/or also have a supplemental source of heat that only comes on during the very coldest periods (oil-fired furnace, natural gas, cast-iron stove, or even resistance heat).

In hot climates you can increase the efficiency of a heat pump by adding water mist, making it a hybrid swamp cooler. Evaporating water will take out a bunch of heat energy.

As was mentioned, insulation is key otherwise you're just spending money on heating or cooling the outdoors. Walls, door, and windows that don't have thermal bridges, controlled air exchange with the outdoors (ERV energy recovery ventilator units), and so on.

Re: The humble water heater could be the savior of our energy infrastructure woes

#160

Post by throw0101a »

paul_f wrote: post #157
cycomanic wrote: post #88

In Northern Europe heat pumps are now pretty much standard for new homes. They reduce heating bills quite dramatically compared to other technology. In particular if combined with solar power. One big advantage is that they can also be run in reverse so you could cool the house in summer (although you might need a special heat pump to do this, especially to separate from the hot water). In areas where it gets very co…

Europe has milder winters than many parts of the world. A downside of a heat pump is the limitation on temperature range. A heat pump could never be used in Minnesota, people would freeze.

> A heat pump could never be used in Minnesota, people would freeze.

Heat pumps work in Alaska:

* https://www.nrel.gov/news/features/2021/even-in-frigid-tempe...

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